// CRC32
//------------------------------------------------------------------------------

// Includes
//------------------------------------------------------------------------------
#include "CRC32.h"

#include "Core/Math/Conversions.h"

// CRC polynomial table
//------------------------------------------------------------------------------
static const uint32_t g_CRC32Table[ 256 ] =
{
    0x00000000,0x77073096,0xEE0E612C,0x990951BA,0x076DC419,0x706AF48F,0xE963A535,
    0x9E6495A3,0x0EDB8832,0x79DCB8A4,0xE0D5E91E,0x97D2D988,0x09B64C2B,0x7EB17CBD,
    0xE7B82D07,0x90BF1D91,0x1DB71064,0x6AB020F2,0xF3B97148,0x84BE41DE,0x1ADAD47D,
    0x6DDDE4EB,0xF4D4B551,0x83D385C7,0x136C9856,0x646BA8C0,0xFD62F97A,0x8A65C9EC,
    0x14015C4F,0x63066CD9,0xFA0F3D63,0x8D080DF5,0x3B6E20C8,0x4C69105E,0xD56041E4,
    0xA2677172,0x3C03E4D1,0x4B04D447,0xD20D85FD,0xA50AB56B,0x35B5A8FA,0x42B2986C,
    0xDBBBC9D6,0xACBCF940,0x32D86CE3,0x45DF5C75,0xDCD60DCF,0xABD13D59,0x26D930AC,
    0x51DE003A,0xC8D75180,0xBFD06116,0x21B4F4B5,0x56B3C423,0xCFBA9599,0xB8BDA50F,
    0x2802B89E,0x5F058808,0xC60CD9B2,0xB10BE924,0x2F6F7C87,0x58684C11,0xC1611DAB,
    0xB6662D3D,0x76DC4190,0x01DB7106,0x98D220BC,0xEFD5102A,0x71B18589,0x06B6B51F,
    0x9FBFE4A5,0xE8B8D433,0x7807C9A2,0x0F00F934,0x9609A88E,0xE10E9818,0x7F6A0DBB,
    0x086D3D2D,0x91646C97,0xE6635C01,0x6B6B51F4,0x1C6C6162,0x856530D8,0xF262004E,
    0x6C0695ED,0x1B01A57B,0x8208F4C1,0xF50FC457,0x65B0D9C6,0x12B7E950,0x8BBEB8EA,
    0xFCB9887C,0x62DD1DDF,0x15DA2D49,0x8CD37CF3,0xFBD44C65,0x4DB26158,0x3AB551CE,
    0xA3BC0074,0xD4BB30E2,0x4ADFA541,0x3DD895D7,0xA4D1C46D,0xD3D6F4FB,0x4369E96A,
    0x346ED9FC,0xAD678846,0xDA60B8D0,0x44042D73,0x33031DE5,0xAA0A4C5F,0xDD0D7CC9,
    0x5005713C,0x270241AA,0xBE0B1010,0xC90C2086,0x5768B525,0x206F85B3,0xB966D409,
    0xCE61E49F,0x5EDEF90E,0x29D9C998,0xB0D09822,0xC7D7A8B4,0x59B33D17,0x2EB40D81,
    0xB7BD5C3B,0xC0BA6CAD,0xEDB88320,0x9ABFB3B6,0x03B6E20C,0x74B1D29A,0xEAD54739,
    0x9DD277AF,0x04DB2615,0x73DC1683,0xE3630B12,0x94643B84,0x0D6D6A3E,0x7A6A5AA8,
    0xE40ECF0B,0x9309FF9D,0x0A00AE27,0x7D079EB1,0xF00F9344,0x8708A3D2,0x1E01F268,
    0x6906C2FE,0xF762575D,0x806567CB,0x196C3671,0x6E6B06E7,0xFED41B76,0x89D32BE0,
    0x10DA7A5A,0x67DD4ACC,0xF9B9DF6F,0x8EBEEFF9,0x17B7BE43,0x60B08ED5,0xD6D6A3E8,
    0xA1D1937E,0x38D8C2C4,0x4FDFF252,0xD1BB67F1,0xA6BC5767,0x3FB506DD,0x48B2364B,
    0xD80D2BDA,0xAF0A1B4C,0x36034AF6,0x41047A60,0xDF60EFC3,0xA867DF55,0x316E8EEF,
    0x4669BE79,0xCB61B38C,0xBC66831A,0x256FD2A0,0x5268E236,0xCC0C7795,0xBB0B4703,
    0x220216B9,0x5505262F,0xC5BA3BBE,0xB2BD0B28,0x2BB45A92,0x5CB36A04,0xC2D7FFA7,
    0xB5D0CF31,0x2CD99E8B,0x5BDEAE1D,0x9B64C2B0,0xEC63F226,0x756AA39C,0x026D930A,
    0x9C0906A9,0xEB0E363F,0x72076785,0x05005713,0x95BF4A82,0xE2B87A14,0x7BB12BAE,
    0x0CB61B38,0x92D28E9B,0xE5D5BE0D,0x7CDCEFB7,0x0BDBDF21,0x86D3D2D4,0xF1D4E242,
    0x68DDB3F8,0x1FDA836E,0x81BE16CD,0xF6B9265B,0x6FB077E1,0x18B74777,0x88085AE6,
    0xFF0F6A70,0x66063BCA,0x11010B5C,0x8F659EFF,0xF862AE69,0x616BFFD3,0x166CCF45,
    0xA00AE278,0xD70DD2EE,0x4E048354,0x3903B3C2,0xA7672661,0xD06016F7,0x4969474D,
    0x3E6E77DB,0xAED16A4A,0xD9D65ADC,0x40DF0B66,0x37D83BF0,0xA9BCAE53,0xDEBB9EC5,
    0x47B2CF7F,0x30B5FFE9,0xBDBDF21C,0xCABAC28A,0x53B39330,0x24B4A3A6,0xBAD03605,
    0xCDD70693,0x54DE5729,0x23D967BF,0xB3667A2E,0xC4614AB8,0x5D681B02,0x2A6F2B94,
    0xB40BBE37,0xC30C8EA1,0x5A05DF1B,0x2D02EF8D
};



// Slicing-by-4 and slicing-by-8 algorithms by Michael E. Kounavis and Frank L. Berry from Intel Corp.
// http://www.intel.com/technology/comms/perfnet/download/CRC_generators.pdf

#define UINT unsigned int
#define RES unsigned int
#define INT int
#define SIZE_T size_t
#define BYTE unsigned char

//#define CRCPOLY 0x82f63b78 // reversed 0x1EDC6F41
#define CRCPOLY 0xEDB88320
#define CRCINIT 0xFFFFFFFF

UINT g_crc_slicing[8][256];

PRAGMA_DISABLE_PUSH_CLANG( "-Wsign-conversion" )

void SlicingInit()
{
    for (UINT i = 0; i <= 0xFF; i++) {
        UINT x = i;
        for (UINT j = 0; j < 8; j++)
            x = (x>>1) ^ (CRCPOLY & (-(INT)(x & 1)));
        g_crc_slicing[0][i] = x;
    }

    for (UINT i = 0; i <= 0xFF; i++) {
        UINT c = g_crc_slicing[0][i];
        for (UINT j = 1; j < 8; j++) {
            c = g_crc_slicing[0][c & 0xFF] ^ (c >> 8);
            g_crc_slicing[j][i] = c;
        }
    }
}

PRAGMA_DISABLE_POP_CLANG // -Wsign-conversion

static RES CRC_SlicingBy8(const BYTE* buf, SIZE_T len)
{
    static bool initialized( false );
    if ( !initialized )
    {
        SlicingInit();
        initialized = true;
    }

    RES crc = CRCINIT;

    // Align to uint32_t boundary
    SIZE_T align = (sizeof(uint32_t) - (size_t)buf) & (sizeof(uint32_t) - 1);
    align = Math::Min(align, len);
    len -= align;
    for (; align; align--)
        crc = g_crc_slicing[0][(crc ^ *buf++) & 0xFF] ^ (crc >> 8);

    PRAGMA_DISABLE_PUSH_CLANG_WINDOWS( "-Wcast-align" )

    SIZE_T nqwords = len / (sizeof(uint32_t) + sizeof(uint32_t));
    for (; nqwords; nqwords--) {
        crc ^= *(const uint32_t*)buf;
        buf += sizeof(uint32_t);
        const UINT next = *(const uint32_t*)buf;
        buf += sizeof(uint32_t);
        crc =
            g_crc_slicing[7][(crc      ) & 0xFF] ^
            g_crc_slicing[6][(crc >>  8) & 0xFF] ^
            g_crc_slicing[5][(crc >> 16) & 0xFF] ^
            g_crc_slicing[4][(crc >> 24)] ^
            g_crc_slicing[3][(next     ) & 0xFF] ^
            g_crc_slicing[2][(next >>  8) & 0xFF] ^
            g_crc_slicing[1][(next >> 16) & 0xFF] ^
            g_crc_slicing[0][(next >> 24)];
    }

    PRAGMA_DISABLE_POP_CLANG_WINDOWS // -Wcast-align

    len &= sizeof(uint32_t) * 2 - 1;
    for (; len; len--)
        crc = g_crc_slicing[0][(crc ^ *buf++) & 0xFF] ^ (crc >> 8);
    return ~crc;
}

// Update
//------------------------------------------------------------------------------
/*static*/ uint32_t CRC32::Update( uint32_t crc32, const void * buffer, size_t len )
{
    const uint8_t * bytes = (const uint8_t*)buffer;
    for ( size_t i = 0; i < len; i++ )
    {
        crc32 = ( crc32 >> 8 ) ^ g_CRC32Table[ ( crc32 ^ bytes[ i ] ) & 0x000000FF ];
    }
    return crc32;
}

// UpdateLower
//------------------------------------------------------------------------------
/*static*/ uint32_t CRC32::UpdateLower( uint32_t crc32, const void * buffer, size_t len )
{
    const uint8_t * bytes = (const uint8_t*)buffer;
    for ( size_t i = 0; i < len; i++ )
    {
        uint8_t b = bytes[ i ];
        if ( ( b >= 'A' ) && ( b <= 'Z' ) )
        {
            b = (uint8_t)( 'a' + ( b - 'A' ) );
        }
        crc32 = ( crc32 >> 8 ) ^ g_CRC32Table[ ( crc32 ^ b ) & 0x000000FF ];
    }
    return crc32;
}

// Calc
//------------------------------------------------------------------------------
/*static*/ uint32_t CRC32::Calc( const void * buffer, size_t len )
{
    return CRC_SlicingBy8( (const unsigned char *)buffer, len );
}

// CalcLower
//------------------------------------------------------------------------------
/*static*/ uint32_t CRC32::CalcLower( const void * buffer, size_t len )
{
    uint32_t crc32 = Start();
    crc32 = UpdateLower( crc32, buffer, len );
    return Stop( crc32 );
}

//------------------------------------------------------------------------------
